Rear view mirrors for use inside automotive vehicles (trucks, passenger cars, etc.) are typically rectangular mirrors of about three by six inches in size located near the front windshield. Such mirrors must be at least this minimum dimension to provide a view of what is taking place behind the vehicle; however with such dimensions the mirrors tend to block a portion of the forward view of the driver. For many combinations of drivers, vehicles and mirrors this blocking of a portion of the forward view is of little consequence. However there are a substantial number of adverse combinations of drivers, vehicles and mirrors in which the forward activity blocked out by the rear view mirror can have serious consequences. The "block-out" problem is particularly serious with compact small-size vehicles when driven by tall people. In such situations the mirror is at or below the driver's eye level and in relatively close proximity to the driver's eye. Accordingly the driver has difficulty in seeing around or under the mirror to view activity starboard of the vehicle.
Conventional mirrors are capable of limited movement up and down for enabling tall or short drivers to obtain a view of the terrain rearwardly of the vehicle. Therefore, by using this mirror adjustment it may be possible to at least partially alleviate the forward blocking problem. However the requirement for rear view performance limits the extent of up-down adjustment that can be effectively utilized.
The block out problem can be overcome by incorporating a periscope system of mirrors into the vehicle roof. However such a system is rather costly and only partially effective from a rear view performance standpoint because the driver is required to shift his eye position to switch from forward viewing to rearward viewing.
It is also known to provide "see-through" semi-transparent mirrors in airplanes and other locations. Such mirrors have a relatively thin semi-transparent silver coating thereon that permits a person to simultaneously see a "forward" image through the semi-transparent film, and also a "rearward" image by way of the reflective surface. Such mirrors are believed to suffer in that the semi-transparent coating cuts down on the intensity of transmitted light and refelcted light; both the direct image and reflected image appear relatively dark and indistinct.
The present invention proposes a relatively low cost solution to the "mirror block-out" problem. In one of its forms the invention comprises a conventional rear view mirror modified so that selected areas thereof are left unsilvered. These unsilvered areas provide see-through apertures that enable the driver to view forward terrain that would otherwise be blocked-out by the mirror. The transparent unsilvered areas are preferably configured as vertical strip-like areas spaced apart by a distance that has a relationship to the average adult person's interpupillary distance, i.e. the distance between the pupils of the driver's left and right eyes. The typical interpupillary distance is about sixty millimeters.
The preferred spacing between transparent areas is such that the driver is enabled to have one eye focused on a reflective surface and the other eye focused on a transparent surface, thereby permitting simultaneous "rearward" viewing and "forward" viewing. The arrangement in effect means that the eye can reconstruct objects behind the mirror as well as objects reflected by the mirror.